What methods or tools have you used to perform assertions in your code?

In C#, the Debug class from the System.Diagnostics namespace is often used for assertion checks. The Debug.Assert method allows you to verify a condition during debugging and display a message if the condition is false. This helps identify errors early in the development process.

Example of usage:

using System.Diagnostics;

int x = 5;
Debug.Assert(x > 0, "Value of x should be positive");

Additionally, for unit testing, frameworks like NUnit or MSTest are used, which provide Assert methods to verify conditions in tests:

Assert.AreEqual(expected, actual);
Assert.IsTrue(condition);

Contract checks can also be used with Code Contracts, but they are less common.